The present disclosure relates generally to electrochemical cells, and in particular to fuel cells having water transport plates.
A typical fuel cell uses the general configuration as is shown in FIG. 1. Hydrogen gas 102 is introduced to the hydrogen electrode (the anode 116), while oxygen, or an oxidant/oxygen-containing gas such as air 104, is introduced to the oxygen electrode (the cathode 114). Water can also be introduced with the hydrogen feed gas 102, such as by humidifying the gas stream. The hydrogen gas for fuel cell operation can originate from a pure hydrogen source, hydrocarbon, methanol, or any other hydrogen source that supplies hydrogen at purity suitable for fuel cell operation (i.e., a purity that does not poison the catalyst or interfere with cell operation). Hydrogen gas 102 electrochemically reacts at the anode 116 to produce protons and electrons, wherein the electrons flow from the anode through an electrically connected external load 120, and the protons migrate through the membrane 118 to the cathode 114. At the cathode 114, the protons and electrons react with oxygen to form water, which additionally includes any water that is dragged through the membrane 118 to the cathode 114. The electrical potential across the anode 116 and the cathode 114 can be exploited to power an external load 120.
In other embodiments, one or more electrochemical cells may be used within a system to both electrolyze water to produce hydrogen and oxygen, and to produce electricity by converting hydrogen and oxygen back into water as needed. Such systems are commonly referred to as regenerative fuel cell systems.
Electrochemical cell systems typically include a number of individual cells arranged in a stack, with the working fluids directed through the cells via input and output conduits or ports formed within the stack structure. The cells within the stack are sequentially arranged, each including a cathode, a proton exchange membrane, and an anode. The cathode and anode may be separate layers or may be integrally arranged with the membrane. Each cathode/membrane/anode assembly (hereinafter “membrane-electrode-assembly”, or “MEA”) typically has a first flow field in fluid communication with the cathode and a second flow field in fluid communication with the anode.
The cells of the stack may be separated by a plate, sometimes referred to as a bipolar plate. The bipolar plate allows for the conduction of electrical current between the cells and in some cases incorporates features, referred to as flow fields that facilitate the movement of fluids within the electrochemical cell system. In some systems, the bipolar plate may incorporate channels that allow for the flow of a coolant (e.g. water) to remove heat from the cells.